LL-37
Also called Human cathelicidin antimicrobial peptide; hCAP18-derived
A natural 37-amino-acid antimicrobial peptide involved in immune defense. A synthetic topical version was tested for leg ulcers, but the larger trial did not find a significant overall benefit.
Overview
What it is
The active peptide cut from the cathelicidin precursor hCAP18, first isolated from white blood cells.
How it works
It kills some microbes in lab tests and influences inflammatory signaling. Its effects depend on context: it helps drive inflammation in psoriasis and promoted lung cancer cell growth in lab and mouse studies.
What the research shows
A 2014 pilot in 34 people with venous leg ulcers found encouraging results at lower concentrations, not the highest. The 2021 HEAL LL-37 trial found no significant healing benefit overall; a possible benefit in larger ulcers needs confirmation.
Studied for
- Venous leg ulcerstopical, mixed
- Antimicrobial activitylab
- Psoriasis and cancer mechanismslab, mouse
Safety and regulatory status
Safety and side effects
Topical trials reported tolerability, but that does not apply to injections. FDA flags immune reactions, impurities and nonclinical concerns about male reproduction and tumor promotion. Trouble breathing, fainting or severe swelling needs urgent care.
Regulatory status
Not FDA approved. On FDA's list of compounding substances with potential safety risks.
Mixing and dosing reference
Reference information only. Read before using this section.
LL-37 (5 mg Vial) Dosage Protocol
- Vial
- 5 mg LL-37
- Add diluent
- 3 mL
- Concentration
- 1.67 mg/mL
- 1 unit (U-100)
- 16.67 mcg in 0.01 mL
- Route
- Subcutaneous
- How often
- Once per day (subcutaneous); optional 5-on/2-off schedule.
- Typical range
- 100–400 µg once daily (gradual titration).
- Cycle length
- 8–12 weeks; optional extension to 16 weeks.
Standard / Gradual Approach
| Week | Daily Dose (µg) | Units (per injection) (mL) |
|---|---|---|
| Week 1 | 50 µg | 3 units (0.03 mL) |
| Week 2 | 100 µg | 6 units (0.06 mL) |
| Week 3 | 150 µg | 9 units (0.09 mL) |
| Week 4 | 200 µg | 12 units (0.12 mL) |
| Week 5 | 250 µg | 15 units (0.15 mL) |
| Week 6 | 300 µg | 18 units (0.18 mL) |
| Week 7 | 350 µg | 21 units (0.21 mL) |
| Week 8 | 400 µg | 24 units (0.24 mL) |
How to mix
- Draw 3.0 mL bacteriostatic water with a sterile syringe.
- Inject slowly down the vial wall; avoid foaming.
- Gently swirl/roll until dissolved (do not shake).
- Label and refrigerate at 2–8 °C (35.6–46.4 °F), protected from light.
Dosing details
- Start: 50–100 µg daily; increase by ~50 µg each week as tolerated.
- Target: 200–400 µg daily by Weeks 4–8.
- Frequency: Once per day (subcutaneous); optional 5-on/2-off schedule.
- Cycle Length: 8–12 weeks; optional extension to 16 weeks.
- Timing: Any consistent time; rotate injection sites.
Storage
- Lyophilized: Store at −20 °C (−4 °F) in dry, dark conditions; follow the product’s validated shelf life.
- Reconstituted: Refrigerate at 2–8 °C (35.6–46.4 °F); do not infer a use-by period or freezing extension without stability data for the exact formulation.
- Allow vials to reach room temperature before opening to reduce condensation uptake.
Administration technique
- Clean the vial stopper and skin with alcohol; allow to dry.
- Pinch a skinfold; insert the needle at 45–90° into subcutaneous tissue.
- Do not aspirate for subcutaneous injections; inject slowly and steadily.
- Rotate sites systematically (abdomen, thighs, upper arms) and move at least 2–3 cm from the previous site.
- Use aseptic technique; always use a new sterile needle and syringe for each injection.
Important notes
- Use new sterile insulin syringes; dispose in a sharps container.
- Rotate injection sites (abdomen, thighs, upper arms) to reduce local irritation.
- Inject slowly; wait a few seconds before withdrawing the needle.
- Document daily dose and site rotation to maintain consistency.
- Early-phase doses (≤10 units) benefit from 30- or 50-unit syringes for precision.
Protocol source: PeptideDosages.com
Common questions
Does LL-37 treat Lyme disease?
No human study supports that.
Is it a general immune booster?
No. Its immune effects can be helpful or harmful depending on context.
The body makes it, so is it safe?
Natural production does not make added doses safe.
Related in Immune Health
Sources and further reading (6)
- Gudmundsson GH, et al. Processing of cathelin precursor to LL-37. Eur J Biochem, 1996.
- Grönberg A, et al. Topical LL-37 in venous leg ulcers: pilot. Wound Repair Regen, 2014.
- Mahlapuu M, et al. LL-37 in venous leg ulcers: randomized trial. Wound Repair Regen, 2021.
- Lande R, et al. Plasmacytoid dendritic cells sense self-DNA with antimicrobial peptide. Nature, 2007.
- FDA. Bulk drug substances with safety risks: LL-37 entry.
- Source summary: PeptideDosages.com research overview (rewritten for NVO).
Laboratory research material: LL37 Research Use Only